Optical module for an objective

ABSTRACT

Disclosed is an optical module for a lens, especially a microlithographic apparatus, comprising a first holding device with an inner circumference that extends in a first circumferential direction, and at least one first supporting device which is fastened to the inner circumference of said first holding device and is used for supporting a first optical element, an annular circumferential first assembly space being defined by displacing the first supporting device once in a revolving manner along the first circumferential direction. At least one second supporting device which is fixed to the inner circumference of the first holding device is provided for supporting a second optical element, an annular circumferential second assembly space being defined by displacing the second supporting device once in a revolving manner along the first circumferential direction. The first assembly space intersects the second assembly space.

BACKGROUND OF THE INVENTION

The present invention relates to an optical module for an objective. Theinvention can be used in connection with microlithography employed inthe production of microelectronic circuits. It further concerns,therefore, an objective barrel which is suitable in particular forapplication in a microlithographic apparatus, as well as such amicrolithographic apparatus including such an objective barrel.

In the field of microlithography in particular, it is necessary for theemployed optical elements of the objective barrel, i.e. the lenses forexample, to be positioned spatially with respect to one another with ashigh a degree of precision as possible, in order to achieve a suitablyhigh image quality. The high precision requirements are not least aconsequence of the constant demand to increase the resolution of opticalsystems used in the production of microelectronic circuits, in order toadvance the miniaturisation of the microelectronic circuits to beproduced.

With the increased resolution, the demands increase on the positioningprecision of the employed optical elements. The latter must bemaintained as far as possible in the installed state over the wholeservice life in order to avoid image errors. Furthermore, there is inthis regard the requirement to achieve a dynamic behaviour of theemployed optical system that is as favourable as possible, with resonantfrequencies that are as high as possible.

For a large number of optical applications, but especially in the fieldof the aforementioned microlithography, objective barrels consisting ofa plurality of optical modules are employed. The individual opticalmodules include as a rule an optical element, such as a lens etc., whichis supported by means of one or more supporting devices at the innercircumference of a holder. Depending on the conditions of the opticalsystem, i.e. amongst other things the optical properties of theobjective that are to be achieved, it is often necessary to positionseveral optical elements closely adjacent one another.

In the case of objectives with one lens per optical module, such as areknown for example from EP 1 168 028 A1, a close arrangement of thelenses is achieved in which the supporting devices with the lenseslocated therein are arranged in a nested manner. This leads on the onehand to comparatively elongated lens barrels. This is due to the factthat the holder of each optical module must have a certain extension inthe direction of the optical axis of the objective barrel in order tohave sufficient strength and rigidity. Furthermore, the spacingrequirement for the lenses together with the axial extension of theholder may give rise to very long supporting devices. These aredisadvantageous particularly from the rigidity standpoint, since this isaccompanied by an undesirably low rigidity and consequently undesirablylow resonant frequencies.

There is proposed in document US 2002/0163741 A1 an arrangement ofoptical modules stacked one upon the other, wherein there is provided inthe given holder a recess for the accommodation of a part of thesupporting devices of the optical module lying thereunder. A reductionin the length of the supporting devices can certainly be achieved bythis means. The recesses, however, in turn cause a weakening andreduction in rigidity of the given holder, and this has to becompensated for, possibly at high cost. On the other hand, this solutionis suitable only for certain designs of the supporting devices.

The object of the present invention, therefore, is to make available anoptical module of the type mentioned at the outset, which does not havethe aforementioned drawbacks or at least only to a lesser extent andguarantees, in particular, a space-saving, rigid arrangement.

BRIEF SUMMARY OF THE INVENTION

The present invention solves this problem with an optical module for anobjective that includes a first holding device with an innercircumference, which extends in a first circumferential direction. Theoptical module also includes at least one first supporting device forsupporting a first optical element and being fixed at the innercircumference of the first holding device. The optical module furtherincludes an annular circumferential first assembly space being definedby displacing the first supporting device once in a revolving manneralong the first circumferential direction. In addition, the opticalmodule includes at least one second supporting device being provided forsupporting a second optical element and being fixed at the innercircumference of the first holding device. Further, the optical moduleincludes an annular circumferential second assembly space being definedby displacing the second supporting device once in a revolving manneralong the first circumferential direction; and the first assembly spaceintersecting the second assembly space. For at least one opticalelement, a mounting device may be provided which is connected detachablyto the end of said at least one supporting device for this opticalelement facing away from said first holding device.

Underlying the present invention is the cognition that, especially inthe case of an arrangement of a plurality of optical elements lyingclose beside one another, a space-saving, rigid arrangement can beachieved if, at the first holding device, at least two optical elementsare supported by, in each case, at least one respective first or secondsupporting device. The supporting devices each define respectively afirst and second annular circumferential assembly space in thecircumferential direction of the holding device. They are arranged insuch a way that the first assembly space intersects the second assemblyspace.

As a result of this arrangement of supporting devices interlaced intoone another or interlocked with one another, respectively, it ispossible for the dimension of the common holding device for both to bekept short in the direction of their central axis. This dimension maypossibly even be smaller than in the case of the support of a singleoptical element by a comparable holding device, since the mounting offurther supporting devices may even contribute towards increasing therigidity of the optical module.

As a result of this compact arrangement, furthermore, the supportingdevices can also be kept as short as possible. This has an advantageouseffect on the mass and the rigidity of the supporting devices and thuson the resonant frequencies of the arrangement.

In other words, compared with the known optical modules, it is possible,with identical rigidity of the arrangement, to achieve a significantreduction in the required assembly space and thus in the mass of theoptical module, as a result of which an advantageous increase in theresonant frequency is obtained.

An object of the present invention, therefore, is an optical module fora lens, in particular for a microlithographic apparatus, which includesa first holding device with an inner circumference which extends in afirst circumferential direction, and at least one first supportingdevice for supporting a first optical element and being connected to theinner circumference of the first holding device. An annularcircumferential first assembly space is defined by displacing the firstsupporting device once in a revolving manner along the firstcircumferential direction. Furthermore, at least one second supportingdevice is provided for supporting a second optical element and beingfixed at the inner circumference of the first holding device. An annularcircumferential second assembly space is defined by displacing thesecond supporting device once in a revolving manner along the firstcircumferential direction. The first assembly space intersects thesecond assembly space.

A further object of the present invention is an objective barrel, inparticular for a microlithographic apparatus, with an optical moduleaccording to the invention.

Finally, a further subject-matter of the present invention is amicrolithographic apparatus for the transfer of a pattern formed on amask onto a substrate using an optical projection system which includesan objective barrel according to the invention.

Further preferred embodiments of the invention will become apparent fromthe dependent claims and the following description of a preferredexample of embodiment, which makes reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional representation of a preferred embodimentof the optical module according to the invention

FIG. 2 is a schematic plan view of the optical module from FIG. 1;

FIG. 3 is a schematic representation of a preferred embodiment of themicrolithographic apparatus according to the invention with an objectivebarrel according to the invention;

FIG. 4 is a schematic sectional representation of a further preferredembodiment of the optical module according to the invention;

FIG. 5 is a schematic plan view of the optical module from FIG. 4;

FIG. 6 is a schematic sectional representation of a further preferredembodiment of the optical module according to the invention;

FIG. 7 is a schematic plan view of the optical module from FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

A first preferred embodiment of the optical module 1 according to theinvention for an objective for microlithography is first described withreference to FIGS. 1 and 2. FIG. 1 shows a diagrammatic sectionalrepresentation of the optical module 1, whilst FIG. 2 shows a schematicplan view of optical module 1 in the direction of module axis 1.1 ofoptical module 1. FIG. 1 is a cross-section along section line I-I fromFIG. 2.

Optical module 1 includes a first holding device in the form of anannular holder 2, which is often referred to as a flange. This holder 2has an inner circumference 2.1, which extends in a first circumferentialdirection 2.2. Three first supporting devices in the form of firstbipods 3.1 (shown in very simplified form) are fixed with one end at theinner circumference 2.1 of the holder 2. First bipeds 3.1 are connectedwith their other end to a first mounting device in the form of a firstmounting 4.1. This first mounting 4.1 in turn carries a first opticalelement in the form of a lens 5.1. Accordingly, the first bloods 3.1thus support the first lens 5.1 via the first mounting 4.1 on the firstholder 2. In other words, the first lens 5.1 is thus fixed via the firstmounting 4.1 and the first bipods 3.1 on the first holder 2.

The first bipods 3.1 each have a first leg 3.11 and a second leg 3.12.The latter are arranged inclined towards one another in their commonplane, so that the respective bipod 3.1 has a central axis 3.13. thefirst bipods 3.1, furthermore, are distributed uniformly at the firstcircumference 2.1 of the holder 2, so that an angle of 120° is enclosedin each case between their first central axes 3.13 in the first plane,which lies parallel to the drawing plane of FIG. 2 and in which thecircumferential direction 2.2 lies.

The first bipods 3.1 together form so-called parallel kinematics in themanner of a hexapod, by means of which the first mounting 4.1 and thusthe first lens 5.1 are positioned spatially with respect to the holder2. The first leg 3.11 and the second leg 3.12 are each fixed to holder 2via a flexure 3.14, 3.15 and 3.16 mobile in the manner of aball-and-socket joint. Each first bipod 3.1 therefore constrains twospatial degrees of freedom, so that a statically determined bearing ofthe first lens 5.1 on the holder 2 is brought about in the form of anisostatic bearing.

Whereas the flexure 3.14 on the mounting side is fixed directly to thefirst mounting 4.1, the two flexures 3.15 and 3.16 on the holder sideare fixed to a first connection element 3.17. The first connectionelement 3.17 is in turn fixed detachably on a first contact element inthe form of a first shoulder 2.3 at the inner circumference 2.1 of theholder 2. The first shoulders 2.3 are all located in a first connectingplane which runs perpendicular to the module axis 1.1. An arbitraryconnection, for example a clamping joint or a screw joint, can beprovided for the connection of the first connection element 3.17 to theholder 2 and the bipods 3.1 to the mounting.

The first shoulder 2.3 extends in the circumferential direction overroughly the same angular range as the first connection element 3.17.Thanks to the detachable connection between the respective connectionelement 3.17 and the respective first shoulder 2.3, it is possible torotate the lens 5.1 about the module axis 1.1 and thus to compensate forimage errors. It is also possible by this means to dismantle the lens5.1 from the holder 2 and, if need be, to subject it to reworking, forexample by means of an ion beam. As a result, an adjustment facilityabout the module axis 1.1 may then become unnecessary, as the case maybe.

In order to be able to position the first lens 5.1 with respect to theholder 2, the first leg 3.11 and the second leg 3.12 arelength-adjustable. In addition, or as an alternative, the position orspacing of at least one mobile part of the respective first leg 3.11 or3.12 can be adjusted with respect to the holder 2. Finally, the axialdistance between the first connection element 3.17 and the firstshoulder 2.3 can be adjusted in the direction of the module axis 1.1. Inany case, these adjustments can take place both by means of passiveelements (e.g. setscrews etc.) and by means of controllable activeelements (eg. piezoelements etc.). It goes without saying, however, thatwith other variants of the invention the supporting devices can, if needbe, also be designed non-adjustable at least in part.

The first lens 5.1 is fixed in the first mounting 4.1 in any suitableway in a positive connection and/or a frictional connection and/or andadhesive connection. Thus, for example, it can be glued, clamped etc.The first mounting 4.1 forms a precisely defined interface between thefirst lens 5.1 and the first bipods 3.1. It goes without saying,however, that with other variants of the invention provision can also bemade such that the first bipods are fixed without the interposition of amounting or the like on the lens.

As can also be seen from FIGS. 1 and 2, the optical module 1 alsoincludes three second supporting devices in the form of second bipods3.2 (also shown in very simplified form). The latter, like the firstbipods 3.1, are each fixed with one end to the inner circumference 2.1of the holder 2 by means of a second connection element 3.27. The secondconnection element 3.27 is again fixed detachably on a second shoulder2.4 at the inner circumference 2.1 of the holder 2. The second shoulders2.4 are all located in a second connecting plane which also runs normalto the module axis 1.1. The second connecting plane lies at a firstdistance below the first connecting plane.

With their other end, the second bipods 3.2 are connected to a secondmounting device in the form of a second mounting 4.2. This secondmounting 4.2 in turn carries a second optical element in the form of asecond lens 5.2. Accordingly, the second bipods 3.2 thus support thesecond lens 5.2 via the second mounting 4.2 on the first holder 2. Inother words, the second lens 5.2 is thus fixed via the second mounting4.2 and the second bipods 3.2 to the first holder 2.

The second bipods 3.2 are designed like the first bipods 3.1 and arefixed to the holder 2 and the second mounting 4.2 respectively, so thatin this regard reference is made to the explanations given above. Inparticular, the second bipods 32 also form so-called parallel kinematicsin the manner of a hexapod, by means of which the second mounting 4.2and thus the second lens 5.2 can be actively positioned spatially withrespect to the holder 2.

Finally, the optical module 1 also includes three third supportingdevices in the form of third bipods 3.3 (also shown in very simplifiedform). The latter, like the first bipods 3.1, are fixed with one end tothe inner circumference 2.1 of the holder 2 by means of a thirdconnection element 3.37. The respective further connection element 3.37is fixed detachably on a third shoulder 2.5 at the inner circumference2.1 of the holder 2. The third shoulders 2.5, like the first shoulders2.3, are all located in the first connecting plane which runs normal tothe module axis 1.1.

With their other end, the third bipods 3.3 are connected to a thirdmounting device in the form of a third mounting 4.3. This third mounting4.3 in turn carries a third optical element in the form of a third lens5.3. Accordingly, the third bipods 3.3 thus support the third lens 5.3via the third mounting 4.3 on the first holder 2. In other words, thethird lens 5.2 is thus fixed via the third mounting 4.3 and the thirdbipods 3.3 to the first holder 2.

The third bipods 3.3 are designed like the first bipods 3.1 and arefixed to the holder 2 and the third mounting 4.3 respectively, so thatin this regard reference is made to the explanations given above. Inparticular, the third bipods 3.3 also form so-called parallel kinematicsin the manner of a hexapod, by means of which the third mounting 4.3 andthus the third lens 5.3 can be actively positioned spatially withrespect to the holder 2.

The first, the second and the third bipods 3.1, 3.2, 3.3 are arranged inthe circumferential direction 2.2 uniformly distributed at innercircumference 2.1 of the holder 2. With a total number of S=9 bipods,the central axes of neighbouring bipeds 3.1, 3.2 and 3.3 are arranged,with respect to the module axis 1.1 in the first circumferentialdirection 2.2, each rotated according to the following equation throughan angle

$\begin{matrix}{\alpha = {\frac{360{^\circ}}{S} = {\frac{360{^\circ}}{9} = {40{^\circ}}}}} & (1)\end{matrix}$

It goes without saying, however, that with other variants of the presentinvention it is also possible for the supporting devices not to bedistributed uniformly in this way at the circumference of the holdingdevice. Particularly in the case of numbers of supporting devicesdiverging from one another for the respective optical element, lessuniform distributions of the supporting devices may be provided ornecessary.

The legs 3.11 and 3.12 of the first bipeds 3.1 each extend both in thedirection of the module axis 1.1 and radially to the latter. Bydisplacing one of the first bipods 3.1 once in a revolving manner at theinner circumference 2.1 of the holder 2 along the first circumferentialdirection 2.2, therefore, an annular circumferential first assemblyspace is defined, as is indicated in FIG. 1 by contour 3.18. The firstassembly space has a shape in the manner of the shell of a truncatedcone. In the present example with a circular holder, the first assemblyspace 3.18 is defined in other words by the toroidal body which ariseswhen one of the first bipods 3.1 is rotated about the module axis 1.1.

The legs 3.21 and 3.22 of the second bipods 3.2 each extend bothslightly in the direction of the module axis 1.1 and also mainlyradially to the latter. By displacing one of the second bipods 3.2 oncein a revolving manner at the inner circumference 2.1 of the holder 2along the first circumferential direction 2.2, therefore, an annularcircumferential second assembly space is also defined, as is indicatedin FIG. 1 by the contour 3.28. The second assembly space 3.28 also has ashape in the manner of the shell of a very flat truncated cone. In thepresent example with a circular holder, the second assembly space 3.28is also defined in other words by the toroidal body which arises whenone of the second bipeds 3.2 is rotated about the module axis 1.1.

The legs 3.31 and 3.32 of the third bipods 3.3 each extend both slightlyin the direction of the module axis 1.1 and also mainly radially to thelatter. By displacing one of the third bipods 3.2 once in a revolvingmanner at the inner circumference 2.1 of the holder 2 along the firstcircumferential direction 2.2, therefore, an annular circumferentialthird assembly space is also defined, as is indicated in FIG. 1 bycontour 3.38. the third assembly space 3.38 also has a shape in themanner of the shell of a very flat truncated cone. In the presentexample with a circular holder, the third assembly space 3.38 is alsodefined in other words by the toroidal body which arises when one of thethird bipods 3.3 is rotated about the module axis 1.1.

The first bipods 3.1 and the second bipods 3.2 are arranged interlockedor interlaced in such a way that the first assembly space 318 and thesecond assembly space 3.28 mutually intersect. The two assembly spaces3.18 and 3.28 penetrate one another in a first penetration region 6.1.In the view of FIG. 2, the first penetration region 6.1 has an annularcontour. the first penetration region 6.1 lies radially with respect tothe module axis 1.1 roughly in the middle between the holder 2 and themountings 4.1 and 4.2.

The first bipods 3.1 and the third bipods 3.3 are arranged interlockedor interlaced in such a way that the first assembly space 3.18 and thethird assembly space 3.38 mutually intersect in the region of theconnection elements 3.17 and 3.37 respectively. They intersect in afirst intersection region 6.2. The latter also has an annular contour inthe view of FIG. 2.

As a result of this design with the penetrating or intersecting assemblyspaces 3.18 and 3.28 or 3.38 respectively, it is possible to keep theheight dimension of the holder 2 short in the direction of the moduleaxis 1.1, although a plurality of lenses 5.1 to 5.3 can be held by theholder 2. An assembly-space and weight reduction can be achieved as aresult. The height dimension may, as the case may be, even be smallerthan in the case where a single optical element is held by a comparableholding device, since the connection of a plurality of supportingdevices may even contribute towards an increase in the rigidity of theoptical module.

As a result of this compact arrangement, moreover, the bipods can alsobe kept as short as possible. This has an advantageous effect on themass and rigidity of the supporting devices and thus on the resonantfrequencies of the arrangement. In other words, in contrast with knownoptical modules, it is possible with the design of the optical module 1according to the invention, with identical rigidity of the arrangement,to achieve a noticeable reduction in the required assembly space andthus in the mass of the optical module 1, as a result of which anadvantageous increase in the resonant frequency of the overallarrangement is obtained.

The arrangement of the first and the third shoulders 2.3 and 2.5 in acommon plane not only reduces the required assembly space. In fact, theproduction of the mounting is also thereby facilitated, since it can beproduced for example from a single circumferential annular shoulder atthe inner circumference 2.1.

The uniform distribution of the bipods 3.1, 3.2, 3.3 at the innercircumference 2.1 of the holder 2 described above ensures, together withtheir fixing at the shoulders 2.3, 2.4 and 2.5 respectively, whichextend only to a limited extent in the circumferential direction 2.2,that the lenses 5.1, 5.2 and 5.3 can be assembled individually.Furthermore, it is possible to assemble or dismantle the lower firstlens 5.1 and the upper third lens 5.3 independently of one another,without one of the other lenses having to be loosened or even removed.Only for the assembly of the middle, second lens 5.2 is it necessary, ofcourse, to remove the first lens 5.1 and the third lens 5.3,respectively.

It goes without saying, however, that in other variants of the inventionthe separate assembly capability of the optical elements can also beensured in any other way by a suitable design and arrangement of theconnection regions between the supporting devices and the holdingdevice.

Furthermore, it goes without saying that in other variants of thepresent invention the supporting devices can also be designeddifferently and be provided in a different number per optical element.In particular, it may be sufficient, with a suitable design, for only asingle supporting device to be provided per optical element. Saidsupporting devices can then extend, as the case may be, over acorrespondingly limited circumferential segment, in order to ensure theinterlocked or interlaced arrangement with the intersection of theassembly spaces. Alternatively, such individual supporting devices canalso extend over the whole circumference of the holding device. Here,suitable perforations for the other supporting device or othersupporting devices must then be provided in order to ensure theinterlocked or interlaced arrangement with the intersection of theassembly spaces.

FIG. 3 shows a diagrammatic representation of a preferred embodiment ofmicrolithographic apparatus 7 according to invention. Microlithographicapparatus 7 includes an optical projection system 8 with a lightingsystem 9, a mask 10 and an objective barrel 11 with an optical objectiveaxis 11.1. The lighting system 9 illuminates a mask 10. On the mask 10is a pattern which is projected via the objective barrel 11 onto asubstrate 12, for example a wafer.

The objective barrel 11 includes a series of barrel modules 11.2 withrefractive, reflective and/or diffractive optical elements such aslenses, mirrors, gratings or the like. The barrel module 11.2 includesthe optical module 1 from FIGS. 1 and 2. the optical module 1 is fixedto a carrier structure 11.21 of the barrel module 11.2.

Second Embodiment

FIGS. 4 and 5 show a schematic representation of a further, secondpreferred embodiment of the optical module 1.01 according to theinvention for an objective for microlithography. FIG. 4 shows across-section along the section line IV-IV from FIG. 5. This embodimentdoes not differ in its basic mode of operation and its basic structurefrom that shown in FIGS. 1 and 2, so that the differences will mainly bedealt with here.

The optical module 101 includes a first holding device in the form of anannular holder 102. This holder 102 has an inner circumference 102.1,which extends in a first circumferential direction 102.2. Three firstsupporting devices in the form of first bipods 103.1 (shown in verysimplified form) are fixed with one end to the inner circumference 102.2of the holder 102. the first bipods 103.1 are connected with their otherend to a first mounting device in the form of a first mounting 104.1.This first mounting 104.1 in turn carries a first optical element in theform of a lens 105.1.

The first bipods 103.1 each have a first leg 103.11 and a second leg103.12. The latter are arranged inclined towards one another in theircommon plane, so that the respective bipod 103.1 has a central axis103.13. The first bipods 103.1 are distributed uniformly at the firstcircumference 102.1 of the holder 102, so that an angle of 120° isenclosed in each case between their first central axes 103.13 in thefirst plane, which is parallel to the drawing plane of FIG. 5 and inwhich circumferential direction 102.2 lies.

The first bipods 103.1 are designed like the first bipods 103.1 fromFIGS. 1 and 2 and are fixed to the holder 102 and the first mounting104.1 respectively. In particular, the first bipods 103.1 are againfixed by means of first connection elements 103.17 detachably on a firstcontact element in the form of a first shoulder 102.3 at the innercircumference 102.1 of the holder 102. The first shoulders 102.3 are alllocated in a first connecting plane which runs perpendicular to themodule axis 1.1.

Like the first bipods 103.1 from FIGS. 1 and 2, the first bipods 103.1form together parallel kinematics in the manner of a hexapod, by meansof which the first mounting 104.1 and thus the first lens 105.1 can beactively positioned spatially with respect to the holder 102 and ismounted isostatically.

As can be seen for FIGS. 4 and 5, furthermore, the optical module 101also includes three second supporting devices in the form of the secondbipods 103.2 (also shown in very simplified form). The latter, like thefirst bipods 103.1, are each fixed with one end to the innercircumference 102.1 of the holder 103 by means of a second connectionelement 103.27. The second connection element 103.27 is again fixeddetachably on a second shoulder 102.4 at the inner circumference 102.1of the holder 102. The second shoulders 102.4 are all also located inthe first connecting plane.

With their other end, the second bipods 103.2 are connected to a secondmounting device in the form of a second mounting 104.2. This secondmounting 104.2 in turn carries a second optical element in the form of asecond lens 105.2. The second bipods 103.2 are designed like the firstbipods 103.1 and are fixed to the holder 102 and the second mounting104.2 respectively, so that in this regard reference is made to theexplanations given above. In particular, the second bipods 103.2 alsoform so-called parallel kinematics in the manner of a hexapod, by meansof which the second mounting 104.2 and thus the second lens 105.2 can beactively positioned spatially with respect to the holder 102.

The second bipods 103.2, furthermore, are also distributed uniformly atthe first circumference 102.1 of the holder 102, so that an angle of120° is enclosed in each case between their second central axes 103.23in the first plane, which is parallel to the drawing plane of FIG. 5 andin which the circumferential direction 2.2 lies.

The first and second bipods 103.1, 103.2, furthermore, are arrangeddistributed in the circumferential direction 102.2 at the innercircumference 102.1 of the holder 102, in such a way that the centralaxes of neighbouring bipods 103.1, 103.2 are each arranged rotatedthrough an angle α=40° with respect to the module axis 101.1 in thefirst circumferential direction 102.2.

The legs 103.11 and 103.12 of the first bipeds 103.1 each extend both inthe direction of the module axis 101.1 and radially to the latter. Bydisplacing one of the first bipods 103.1 once in a revolving manner atthe inner circumference 102.1 of the holder 102 along the firstcircumferential direction 102.2, therefore, an annular circumferentialfirst assembly space is defined, as is indicated in FIG. 4 by thecontour 103.18. The first assembly space has a shape in the manner ofthe shell of a truncated cone. In the present example with a circularholder, the first assembly space 103.18 is defined in other words by thetoroidal body which arises when one of the first bipods 103.1 is rotatedabout the module axis 101.1.

The legs 103.21 and 103.22 of the second bipods 103.2 each extend bothslightly in the direction of the module axis 101.1 and radially to thelatter. By displacing one of the second bipods 103.2 once in a revolvingmanner at the inner circumference 102.1 of the holder 102 along firstcircumferential direction 102.2, therefore, an annular circumferentialsecond assembly space is also defined, as is indicated in FIG. 4 by thecontour 103.28. The second assembly space 103.28 also has a shape in themanner of the shell of a truncated cone. In the present example with acircular holder, the second assembly space 103.28 is also defined inother words by the toroidal body which arises when one of the secondbipeds 103.2 is rotated about the module axis 101.1.

Apart from the number of lenses carried by the optical module 101, theessential difference from the embodiment shown in FIGS. 1 and 2 consistsin fact that the first bipods 103.1 and the second bipeds 103.2 areorientated in such a way that the first lens 105.1 is held above thefirst connecting plane, whilst the second lens 105.2 is held below thefirst connecting plane.

The first bipods 103.1 and the second bipods 103.2 are also arrangedinterlocked or interlaced in such a way that the first assembly space103.18 and the second assembly space 103.28 mutually intersect. Thefirst intersection region 106.1 has an annular contour in the view ofFIG. 5.

As a result of this design with intersecting assembly spaces 103.18 and103.28, it is possible to keep the height dimension of the holder 102short in the direction of the module axis 101.1, although a plurality oflenses 105.1 to 105.3 are held by the holder 102. An assembly-space andweight reduction as well as an increase in the resonant frequency of theoverall arrangement can be achieved by this means, as already describedin detail above. By the arrangement of the lenses 105.1 and 105.2respectively above and below the first connecting plane, it is possiblein particular to achieve a very compact arrangement with very shortbipods 103.1 and 103.2.

The arrangement of the first and third shoulders 102.3 and 102.4 in acommon plane again not only reduces the required assembly space. Infact, the production of the mounting 102 is also thereby facilitated,since it can be produced for example from a single circumferentialannular shoulder at the inner circumference 102.1.

The optical module 101 can be used instead of any optical module, e.g.instead of the optical module 1, in the microlithographic apparatus fromFIG. 3.

Third Embodiment

FIGS. 6 and 7 show schematic representations of a third preferredembodiment of the optical module 201 according to the invention for anobjective for microlithography. FIG. 6 is a cross-section along thesection line VI-VI from FIG. 7. This embodiment does not differ in itsbasic mode of operation and its basic structure from that shown in FIGS.1 and 2, so that the differences will mainly be dealt with here.

The optical module 201 includes a first holding device in the form of anannular holder 202. This holder 202 has an inner circumference 202.1,which extends in a first circumferential direction 202.2. Three firstsupporting devices in the form of active first bipods 203.1 (shown invery simplified form) are fixed with one end to the inner circumference202.1 of the holder 202. The first bipods 203.1 are connected with theirother end directly to a first optical element in the form of a mirror205.1.

The first bipods 203.1 each have a first leg 203.11 and a second leg203.12. The latter are arranged inclined towards one another in theircommon plane, so that the respective bipod 203.1 has a first centralaxis 203.13. The first bipods 203.1 are distributed uniformly at thefirst circumference 202.1 of the holder 202, so that an angle of 120° isenclosed in each case between their first central planes 203.13, whichrun perpendicular to the drawing plane of FIG. 7, in the first planeparallel to the drawing plane of FIG. 7 in which the circumferentialdirection 202.2 lies.

The respective first bipod 203.1 is, as mentioned, connected directly tothe first mirror 205.1, i.e. without an interposed mounting or the like.For this purpose, the first mirror 205.1 has three radial projections205.11, to which the legs 203.11 and 203.12 of the respective firstbipod 203.1 are fixed.

The first bipods 203.1 are in principle designed like the first bipods203.1 from FIGS. 1 and 2 and are fixed to the holder 202 and the firstmirror 205.1, respectively. In particular, the first bipods 203.1 areagain fixed detachably at the inner circumference 202.1 of the holder202 by means of first connection elements 203.17. The first connectionelements 203.17 are all located in a first connecting plane which runsperpendicular to the module axis 201.1. The first connection elements203.7 can be connected to the holder 202 for example by means of screwjoints, clamping joints or the like acting in the radial direction ofthe holder 202.

Like the first bipeds 3.1 shown in FIGS. 1 and 2, the first bipods 203.1form together so-called parallel kinematics in the manner of a hexapod,by means of which the first mirror 205.1 can be actively positionedspatially with respect to the holder 202 and is mounted isostatically.

As can also be seen from FIGS. 6 and 7, the optical module 201 alsoincludes three second supporting devices in the form of active secondbipods 203.2 (also shown in very simplified form). The latter, like thefirst bipods 203.1, are each fixed with one end at the innercircumference 202.1 of the holder 203 by means of a second connectionelement 203.27. The second connection elements 203.27 can be connecteddetachably to the holder 202, once again for example by means of screwjoints, clamping joints are suchlike acting in the radial direction ofthe holder 202. The second connection elements 203.27 are all located ina second connecting plane.

With their other end, the second bipods 203.2 are connected directly,i.e. without an interposed mounting or the like, to a second opticalelement in the form of a second mirror 205.2. For this purpose, thesecond mirror 205.2 also has three radial projections 205.21, to whichthe legs 203.21 and 203.22 of the respective second bipod 203.2 arefixed.

The second bipods 203.2 are designed like the first bipods 203.1 and arefixed to the holder 202 and the second mirror 205.2 respectively, sothat in this regard reference is made to the explanations given above.In particular, the second bipods 203.2 also form so-called parallelkinematics in the manner of a hexapod, by means of which the secondmirror 205.2 can be actively positioned spatially with respect to theholder 202.

Furthermore, the second bipods 203.2 are also uniformly distributed atthe first circumference 202.1 of the holder 202, so that an angle of120° is enclosed in each case between their second central planes203.23, which run perpendicular to the drawing plane of FIG. 7, in thefirst plane parallel to the drawing plane of FIG. 7, in which thecircumferential direction 202.2 lies.

Furthermore, the first and second bipods 203.1, 203.2 are arranged, inthe circumferential direction 202.2, uniformly distributed at innercircumference 202.1 of the holder 202, so that the central planes ofneighbouring bipods 203.1, 203.2 are arranged, with respect to themodule axis 201.1 in the first circumferential direction 202.2, eachrotated according to the above equation (1) through an angle α=60°.

The legs 203.11 and 203.12 of the first bipods 203.1 each extend both inthe direction of the module axis 201.1 and tangentially to the firstcircumferential direction 202.2. By displacing one of the first bipeds203.1 once in a revolving manner at the inner circumference 202.1 of theholder 202 along the first circumferential direction 202.2, therefore,an annular circumferential first assembly space is defined, as isindicated in FIG. 6 by the contour 203.18. The first assembly space hasa shape in the manner of the shell of a cylinder. In the present examplewith an annular holder, the first assembly space 203.18 is defined inother words by the toroidal body which arises when one of the firstbipods 203.1 is rotated about the module axis 201.1.

The legs 203.21 and 203.22 of the second bipods 203.2 each extend bothslightly in the direction of the module axis 201.1 and tangentially tothe first circumferential direction 202.2. By displacing one of thesecond bipeds 203.2 once in a revolving manner at the innercircumference 202.1 of the holder 202 along the first circumferentialdirection 202.2, therefore, an annular circumferential second assemblyspace is also defined, as is indicated in FIG. 6 by contour 203.28. Thesecond assembly space 203.28 also has a shape in the manner of the shellof a cylinder. In the present example with a circular holder, the secondassembly space 203.28 is also defined in other words by the toroidalbody which arises when one of the second bipods 203.2 is rotated aboutthe module axis 201.1.

Apart from the number of mirrors carried by the optical module 201, anessential difference from the embodiment shown in FIGS. 1 and 2 consistsin fact that the first bipods 203.1 and the second bipods 203.2 areorientated in such a way that the first mirror 205.1 is held below thefirst connecting plane, whilst the second mirror 205.2 is held above thesecond connecting plane, which in turn lies below the first connectingplane.

A further difference consists in the fact that the first bipods 203.1and the second bipods 203.2 are orientated in such a way that a cylindershell-shaped first assembly space 203.18 and a cylinder jacket-shapedsecond assembly space 203.28 coaxial thereto and of essentially the samediameter are defined. The first bipods 203.1 and the second bipods 203.2are arranged interlocked or interlaced in such a way that the firstassembly space 203.18 and the second assembly space 203.28 mutuallyintersect or penetrate. The first intersection region 206.1 also has acylinder shell-shaped contour. The first assembly space 203.18 and thesecond assembly space 203.28 in other words penetrate one another insuch a way that they essentially overlap one another over a widesection. This produces a particularly space-saving supporting structure,which also enables the assembly of optical elements of large diameterinto an objective barrel of predetermined internal diameter.

As a result of this design with the penetrating assembly spaces 203.18and 203.28, it is possible to keep the height dimension of holder 202short in the direction of the module axis 201.1, although a plurality ofthe mirrors 205.1 to 205.3 are held by the holder 202. An assembly-spaceand weight reduction as well as an increase in the resonant frequency ofthe overall arrangement can be achieved by this means, as alreadydescribed in detail above. By the arrangement of the mirrors 205.1 and205.2 respectively above and below the assigned connecting plane, it ispossible in particular to achieve a very compact arrangement with veryshort bipods 203.1 and 203.2.

The first mirror 205.1 has a reflecting first face 205.12 and a firstthrough hole 205.13. The same applies to the second mirror 205.1, whichhas a reflecting second face 205.22 and a second through hole 205.23.The mirrors 205.1 and 205.2 are held in such a way that their reflectingfaces 205.12 and 205.22 are facing towards one another. The throughholes 205.13 and 205.23 ensure that the useful light can first passthrough the first perforation 205.13 into the space between thereflecting faces 205.12 and 205.22, is deflected by the reflecting firstface 205.12 onto the second reflecting face 205.22 and from the lattercan leave the space between the reflecting faces 205.12 and 205.22through the second through hole 205.23. In this way, it is possible toachieve a very compact catadioptric arrangement in an extremely narrowspace.

In the same way as in the second embodiment, the optical module 201 canbe used instead of any optical module, in particular in place of theoptical module 1, in the microlithographic apparatus from FIG. 3.

The present invention has been described above solely with the aid ofexamples, wherein optical elements of the same kind are held in a singleoptical module. It goes without saying, however, that the presentinvention can also be used for any combinations of optical elements ofdifferent kinds which are held in a single optical module.

The present invention has also been described above solely with the aidof examples from the area of objectives for microlithography. It goeswithout saying, however, that the present invention can also be used forany other objectives.

1.-23. (canceled)
 24. An optical module comprising: a first holdingdevice with a circumference extending in a first circumferentialdirection; and a plurality of first supporting devices configured tosupport a first optical element, the first supporting devices beingfixed at the circumference of the first holding device, wherein: alongthe first circumferential direction, at least one of the firstsupporting devices is located in a non-equidistant manner between twoneighboring first supporting devices; and the optical module isconfigured to be used in a microlithography objective.
 25. The opticalmodule of claim 24, wherein the first optical element has a shapeselected from a group consisting of a shape asymmetric along the firstcircumferential direction, a shape non rotationally symmetric along thefirst circumferential, a shape having a recess forming a light passage,and a shape having recess causing an asymmetry of the optical element.26. The optical module of claim 24, further comprising a plurality ofsecond supporting devices, wherein: the second supporting devices areconfigured to support a second optical element; the second supportingdevices are fixed at a circumference of the first holding device; thefirst supporting devices do not contact the second supporting devices;and the first optical element is separate from the second opticalelement, or the first optical element is non-contiguous with the secondoptical element.
 27. The optical module of claim 26, wherein, along thefirst circumferential direction, one of the first supporting devices islocated in a non-equidistant manner between two neighboring secondsupporting devices.
 28. The optical module of claim 26, wherein: a firstassembly space is defined by a first shell formed if the firstsupporting devices were displaced through 360° about a central axis andalong the first circumferential direction; a second assembly space isdefined by a second shell formed if the second supporting devices weredisplaced through 360° along the first circumferential direction; andthe outer surface of the first shell intersects the outer surface of thesecond shell so that the first assembly space one of intersects andpenetrates the second assembly space.
 29. The optical module of claim28, further comprising at least one third supporting device configuredto support a third optical element, wherein the at least one thirdsupporting device is fixed at a circumference of the first holdingdevice, a third assembly space is defined by a third shell formed if theat least one third supporting device were displaced through 360° alongthe first circumferential direction, and the third assembly spaceintersects at least one of the first assembly space and the secondassembly space.
 30. The optical module of claim 28, wherein: the firstshell has an outer surface having a first end located at thecircumference of the first holding device at a first level along thecentral axis and a second end located adjacent the first optical elementat a second level along the central axis; the second end of the firstshell is opposite the first end of the first shell and the second levelbeing spaced from the first level along the central axis; the secondshell has an outer surface having a first end located at thecircumference of the first holding device and a second end adjacent thesecond optical element; and the second end of the second shell isopposite the first end of the second shell.
 31. The optical module ofclaim 28, wherein the first shell is in the shape of a truncated cone,and the second shell is in the shape of a truncated cone.
 32. Theoptical module of claim 28, wherein the first shell is in the shape of acylinder, and the second shell is in the shape of a cylinder.
 33. Theoptical module of claim 28, wherein the first shell is in the shape of atoroidal body, and the second shell is in the shape of a toroidal body.34. The optical module of claim 26, wherein the first circumferentialdirection lies in a first plane and at least one of the following holds:at least one device selected from the group consisting of the at leastone first supporting device and at least one of the second supportingdevices extends at least in a first direction which runs perpendicularto the first circumferential direction in the first plane; and at leastone device selected from the group consisting of the at least one firstsupporting device and at least one of the second supporting devicesextends at least in a second direction which runs perpendicular to thefirst plane.
 35. The optical module of claim 26, wherein at least onesupporting device is fixed detachably to the first holding device, theat least one supporting device being selected from the group consistingof one of the first supporting devices, one of the second supportingdevices, and a combination thereof.
 36. The optical module of claim 35,wherein the at least one supporting device includes at least oneconnection element for the connection of the at least one supportingdevice to the first holding device.
 37. The optical module of claim 26,wherein: at least one of the first supporting devices is connected to afirst contact element of the first holding device, at least one of thesecond supporting devices is connected to a second contact element ofthe first holding device, the first contact element and the secondcontact element being arranged substantially in a common second plane,which runs parallel to a first plane in which the first circumferentialdirection lies.
 38. The optical module of claim 26, wherein at least onesupporting device is fixed to the first holding device so as to beadjustable, the at least one supporting device being selected from thegroup consisting of the at least one first supporting device, at leastone of the second supporting devices, and a combination thereof.
 39. Theoptical module of claim 26, wherein at least one supporting device isdesigned for the adjustment of the position of the optical elementsupported by the at least one supporting device, the at least onesupporting device being selected from the group consisting of one of thefirst supporting devices, at least one of the second supporting devices,and a combination thereof.
 40. The optical module of claim 26, wherein,for at least one optical element, a plurality of the first and secondsupporting devices are fixed to the first holding device and aredesigned for a statically determined support of the at least one opticalelement.
 41. The optical module of claim 26, wherein at least onesupporting device is designed in the manner of a bipod, the at least onesupporting device being selected from the group consisting of one of thefirst supporting devices, one of the second supporting devices, and acombination thereof.
 42. The optical module of claim 26, furthercomprising a mounting device for at least one optical element selectedfrom the group consisting of the first optical element and the secondoptical element, wherein the mounting device is connected detachably tothe end of at least one supporting device for the at least one opticalelement facing away from the first holding device, and the at least onesupporting device is selected from the group consisting of one of thefirst supporting devices, one of the second supporting devices, and acombination thereof.
 43. The optical module of claim 26, wherein: atleast one optical element is supported by at least one supporting deviceon the holding device; the at least one supporting device is selectedfrom the group consisting of one of the first supporting devices, one ofthe second supporting devices, and a combination thereof; and the atleast one optical element is selected from the group consisting of thefirst optical element and the second optical element.
 44. The opticalmodule of claim 43, wherein the at least one optical element isconnected directly to the end of the at least one supporting device forthe at least one optical element facing away from the first holdingdevice.
 45. The optical module of claim 43, wherein the at least oneoptical element is a reflecting element.
 46. The optical module of claim43, wherein the at least one optical element has a projection, which isconnected to the end of the at least one supporting device for the atleast one optical element facing away from the first holding device. 47.The optical module of claim 26, wherein the first optical element isreflective, and the second optical element is reflective.
 48. Theoptical module of claim 47, wherein: the first optical element has areflecting first face; the second optical element has a reflectingsecond face, the first optical element and second optical elements arearranged directly adjacent to one another; and the reflecting first facefaces the reflecting second face.
 49. The optical module of claim 47,wherein the first optical element has an optical surface reflectinglight directly onto an optical surface of the second optical element.50. The optical module of claim 26, wherein one of the first supportingdevices is a first bipod.
 51. The optical module of claim 50, whereinthe at least one second supporting device is a second bipod.
 52. Theoptical module of claim 24, wherein: the optical module has a totalnumber S of the first and second supporting devices fixed at acircumference of the first holding device; the total number S of thefirst and second supporting devices includes the first supportingdevices and the second supporting devices; one of the total number S ofthe first and second supporting devices is displaced with respect to aneighboring one of the total number S of the first and second supportingdevices by an angle which is one of 40° and not equal to$\alpha = \frac{360{^\circ}}{S}$ with respect to a central axis of thefirst holding device in the first circumferential direction; the centralaxis runs perpendicular to a first plane in which the firstcircumferential direction lies.